1. Field of the Invention
The present invention relates to a device for preventing fuel vapor from escaping to the outside air from a fuel tank.
2. Description of the Related Art
A motor vehicle driven by an internal combustion engine is normally equipped with a fuel tank. When it becomes necessary to replenish the fuel tank with fuel, the cap attached to the fuel inlet of the fuel tank must first be detached, to allow the insertion of a fuel pump nozzle. After the fuel pump nozzle is inserted into the fuel inlet of the fuel tank, fuel is fed into the fuel tank from the fuel pump nozzle. However, when the level of the surface in the fuel tank is low, the space in the fuel tank above the surface of the liquid fuel is filled with a large amount of fuel vapor under pressure. Consequently, when the cap is detached from the fuel inlet of the fuel tank, the fuel vapor in the fuel tank is forced out of the fuel tank into the outside air, causing air pollution. In addition, when fuel is fed into the fuel tank from the fuel pump nozzle, the fuel spouted from the nozzle comes into violent contact with and agitates the fuel in the fuel tank, causing bubbles to form in the fuel in the fuel tank. The collapsing of these bubbles causes further amounts of fuel vapor to be generated in the fuel tank, and this fuel vapor also escapes from the fuel inlet of the fuel tank, causing more air pollution.